Applied Energy, Vol.238, 683-695, 2019
Increasing osmotic power and energy with maximum power point tracking
A feedback control system is developed for coordinated control of feed rates, draw rates, and loading on an osmotic power system. Carefully balancing these parameters in order to reduce the overall effect of various non ideal phenomena has been previously discussed in the literature, however this is the first-ever system developed for automated, real-time, simultaneous control of all three of these operating parameters. The ability of the system to achieve maximum net power output is demonstrated for various commercial membranes, in response to fouling, and for both stand-alone pressure retarded osmosis as well as for combined reverse osmosis and pressure retarded osmosis application. Results provide insight into best operating conditions which can be helpful for rule of thumb design, and also clearly show that best conditions are case specific, and that osmotic energy conversion systems ultimately require feedback control for efficient performance especially in response to dynamic phenomena such as membrane fouling. The tradeoff between net power and energy is also demonstrated, and a maximum energy controller is also described.